Massive Ice Cloud on Saturn's Titan Heralds Winter on the Icy World

First Posted: Nov 13, 2015 08:16 AM EST

NASA's Cassini spacecraft has made a surprising discovery about Saturn's moon, Titan. It's discovered a truly massive ice cloud on the moon, heralding the change of seasons on the world.

Cassini's camera already imaged what appeared to be an impressive cloud hovering over Titan's south pole at an altitude of about 186 miles. However, that cloud, first seen in 2012, turned out to be just the tip of the iceberg. Now, researchers have found a much more massive ice cloud system lower in the stratosphere, peaking at an altitude of about 124 miles.

The new cloud was detected by Cassini's infrared instrument, the Composite Infrared Spectrometer (CIRS). This instrument obtains profiles of the atmosphere at invisible thermal wavelengths. In this case, the cloud has a low density similar to Earth's fog, but likely flat on top.

"When we looked at the infrared data, this ice cloud stood out like nothing we've ever seen before," said Carrie Anderson, one of the researchers, in a news release. "It practically smacked us in the face."

The ice clouds at Titan's poles actually don't form the same way as Earth's familiar rain clouds. For rain clouds, water evaporates from the surface and encounters cooler temperatures as it rises through the troposphere. Clouds form when the water vapor reaches an altitude where the combination of temperature and air pressure is right for condensation. The methane clouds in Titan's troposphere form in a similar way.

However, Titan's polar clouds form higher in the atmosphere by a different process. Circulation in the atmosphere transports gases from the pole in the warm hemisphere to the pole in the cold hemisphere. At the cold pole, the warm air sinks, rather like water draining from a bathtub, in a process known as subsidence.

"Titan's seasonal changes continue to excite and surprise," said Scott Edgington, one of the researchers. "Cassini, with its very capable suite of instruments, will continue to periodically study how changes occur on Titan until its Solstice mission ends in 2017."

For more information about the Cassini mission, visit NASA's website.

NASA Cassini Spacecraft Flies by Icey, Oceanic World, Enceladus

For more great science stories and general news, please visit our sister site, Headlines and Global News (HNGN).

See Now: NASA's Juno Spacecraft's Rendezvous With Jupiter's Mammoth Cyclone

TagsNASA, NASA’s, Saturn, Titan, Weather, Cassini, Cassini Spacecraft, Moon